Method of cleaning plant parts for the preparation or processing of (meth)acrylic esters

Abstract

Plant parts which are used for the production or processing of (meth)acrylic esters are cleaned by (a) emptying the plant parts, (b) flushing the plant parts with aqueous 5 to 50% strength by weight alkali metal hydroxide solution, (c) removing the alkali metal hydroxide solution from the plant parts, (d) if required, washing the plant parts with water and (e) if required, drying the plant parts.

We claim:  
     
       1. A method for cleaning plant parts for producing or processing (meth)acrylic esters, which comprises the steps of: 
       a) emptying plant parts in which producing or processing of (meth)acrylic esters has been carried out;  
       b) flushing the plant parts with aqueous 5 to 30% strength by weight of alkali metal hydroxide solution, which solution consists of water and sodium hydroxide; and  
       c) removing the sodium hydroxide solution from the plant parts.  
     
     
       2. The method of  claim 1 , which further comprises the step of: 
       d) washing the plant parts of step c) with water.  
     
     
       3. The method of  claim 2 , which further comprises the step of: 
       e) drying the plant parts of step d).  
     
     
       4. The method of  claim 1 , wherein said sodium hydroxide solution has a strength of from 10 to 30% by weight. 
     
     
       5. The method of  claim 1 , wherein the sodium hydroxide solution has a temperature of from 20 to 140° C. during the flushing. 
     
     
       6. The method of  claim 5 , wherein the temperature of the sodium hydroxide solution during the flushing is 60 to 100° C. 
     
     
       7. The method of  claim 1 , wherein the plant parts are selected from the group consisting of reactors, distillation columns, extraction apparatii, heat exchangers, evaporators, condensers, pipes and pumps, which are optionally connected to form a unit. 
     
     
       8. The method of  claim 7 , wherein said plant parts are connected to form a unit, the unit comprising a distillation unit which has a flushing line between the evaporator and the top of the columns. 
     
     
       9. The method of  claim 1 , wherein the plant parts are cleaned to remove deposited polymers formed in the producing or processing of (meth)acrylic esters. 
     
     
       10. The method of  claim 8 , wherein alcohols containing the alkali metal hydroxide solution after step c) are separated from said solution by phase separation, distillation or stripping and, optionally, are recycled to an esterification for the production of (meth)acrylic esters. 
     
     
       11. A The method of  claim 1 , wherein the alkali metal hydroxide solution is collected after the flushing and used several times thereafter for further cleaning. 
     
     
       12. The method of  claim 1 , wherein the plant parts are cleaned to remove residues from the production of (meth)acrylic esters by reaction of (meth)acrylic acid with alcohols or olefins or by reacting (meth)acrylic esters with alcohols. 
     
     
       13. The method of  claim 4 , wherein said sodium hydroxide solution has a strength of 20% by weight. 
     
     
       14. The method of  claim 1 , wherein said flushing of step b) is effected for from 1 to 24 hours. 
     
     
       15. The method of  claim 9 , wherein said plant parts are cleaned to remove deposited polymers formed in the producing or processing of butyl acrylate.